From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: perf: use-after-free in perf_release
Date: Tue, 14 Mar 2017 14:47:15 +0100 [thread overview]
Message-ID: <20170314134715.GF3328@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20170314132427.GA27369@redhat.com>
On Tue, Mar 14, 2017 at 02:24:27PM +0100, Oleg Nesterov wrote:
> On 03/14, Peter Zijlstra wrote:
> >
> > On Tue, Mar 07, 2017 at 05:51:32PM +0100, Oleg Nesterov wrote:
> >
> > > inherit_event() returns NULL under is_orphaned_event() check, not ERR_PTR().
> > > Is it correct?
> >
> > Yes. This is all a tad tricky, but it seems to be correct.
> >
> > By returning NULL, not an error, we affect the silent discard of
> > orphaned events. This is correct, because otherwise
> > perf_event_release_kernel() would have come by and explicitly discarded
> > those events for us anyway.
>
> Thanks... I'll try to understand this later.
>
> > @@ -10608,7 +10627,6 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
> > * First allocate and initialize a context for the
> > * child.
> > */
> > -
> > child_ctx = alloc_perf_context(parent_ctx->pmu, child);
> > if (!child_ctx)
> > return -ENOMEM;
> > @@ -10670,7 +10688,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
> > ret = inherit_task_group(event, parent, parent_ctx,
> > child, ctxn, &inherited_all);
> > if (ret)
> > - break;
> > + goto out_unlock;
> > }
> >
> > /*
> > @@ -10686,7 +10704,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
> > ret = inherit_task_group(event, parent, parent_ctx,
> > child, ctxn, &inherited_all);
> > if (ret)
> > - break;
> > + goto out_unlock;
>
> With this change you can also simplify inherit_task_group() a little bit,
> it no longer needs to nullify *inherited_all if inherit_group() fails.
Ah, that last one is broken because then we forget to re-enable
parent_ctx->rotate_disable.
So if we keep that a break, we still need that inherited_all thing as
well.
next prev parent reply other threads:[~2017-03-14 13:47 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-06 9:57 perf: use-after-free in perf_release Dmitry Vyukov
2017-03-06 12:13 ` Peter Zijlstra
2017-03-06 12:17 ` Dmitry Vyukov
2017-03-06 12:23 ` Peter Zijlstra
2017-03-06 12:27 ` Dmitry Vyukov
2017-03-06 12:47 ` Peter Zijlstra
2017-03-06 13:14 ` Peter Zijlstra
2017-03-06 13:34 ` Dmitry Vyukov
2017-03-07 9:08 ` Peter Zijlstra
2017-03-07 9:26 ` Dmitry Vyukov
2017-03-07 9:37 ` Peter Zijlstra
2017-03-07 9:43 ` Dmitry Vyukov
2017-03-07 10:00 ` Peter Zijlstra
2017-03-07 13:16 ` Peter Zijlstra
2017-03-07 13:27 ` Peter Zijlstra
2017-03-07 14:04 ` Oleg Nesterov
2017-03-07 14:17 ` Dmitry Vyukov
2017-03-07 16:51 ` Oleg Nesterov
2017-03-07 17:29 ` Peter Zijlstra
2017-03-14 12:55 ` Peter Zijlstra
2017-03-14 13:24 ` Oleg Nesterov
2017-03-14 13:47 ` Peter Zijlstra [this message]
2017-03-14 14:03 ` Oleg Nesterov
2017-03-14 14:07 ` Peter Zijlstra
2017-03-14 14:30 ` Oleg Nesterov
2017-03-14 15:02 ` Peter Zijlstra
2017-03-14 15:07 ` Peter Zijlstra
2017-03-14 15:37 ` Oleg Nesterov
2017-03-14 15:46 ` Peter Zijlstra
2017-03-14 15:19 ` Oleg Nesterov
2017-03-14 15:26 ` Peter Zijlstra
2017-03-14 15:59 ` Peter Zijlstra
2017-03-15 16:43 ` Oleg Nesterov
2017-03-16 12:05 ` Peter Zijlstra
2017-03-16 13:57 ` Peter Zijlstra
2017-03-16 16:41 ` Oleg Nesterov
2017-03-16 12:47 [PATCH 0/4] perf patches Peter Zijlstra
2017-03-16 12:47 ` [PATCH 1/4] perf: Fix use-after-free in perf_release() Peter Zijlstra
2017-03-16 15:19 ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 12:47 ` [PATCH 2/4] perf: Fix event inheritance on fork() Peter Zijlstra
2017-03-16 15:19 ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 12:47 ` [PATCH 3/4] perf: Simplify perf_event_free_task() Peter Zijlstra
2017-03-16 15:20 ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 12:47 ` [PATCH 4/4] perf: Better explain the inherit magic Peter Zijlstra
2017-03-16 15:21 ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 13:20 ` [PATCH 0/4] perf patches Ingo Molnar
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